The invention discloses a construction method of bridge guardrail reinforcement. The construction method comprises the steps that the number and size of the guardrail reinforcement is calculated and determined; a locating frame of the guardrail reinforcement is welded to a pedestal of a site on which the guardrail reinforcement needs to be installed, the guardrail reinforcement is welded accordingto the locating frame of the guardrail reinforcement, and locating is carried out through a reinforcement linear control device. According to the construction method of the bridge guardrail reinforcement, the locating accuracy of the guardrail reinforcement is improved, the installation time of the guardrail reinforcement is saved, and the accuracy of the height of the guardrail reinforcement isimproved.